What is the best pipe material for a drinking water distribution network?

in most cirstances, PVC. It is inert with water, so it won't leave trace elements or oxides in the water, and it can be made extremely smooth so there are minimal friction losses along the length of the pipe. And it's cheaper to produce than most of the other options. It won't allow contaminants into the drinking water supply. And I'm sure there are other reasons. The only downside is if you have a very high pressure network, PVC isn't as strong as metal pipes, but this is the exception rather than the rule